S.
Sagaret on grafts, 262.
Salmons, males fighting, and hooked jaws of, 88.
Salt-water, how far injurious to seeds, 358.
Saurophagus sulphuratus, 183.
Schiödte on blind insects, 138.
Schlegel on snakes, 144.
Sea-water, how far injurious to seeds, 358.
Sebright, Sir J., on crossed animals, 20.
——, on selection of pigeons, 31.
Sedgwick, Prof., on groups of species suddenly appearing, 302.
Seedlings destroyed by insects, 67.
Seeds, nutriment in, 77.
——, winged, 146.
——, power of resisting salt-water, 358.
—— in crops and intestines of birds, 361.
—— in mud, 386.
——, hooked, on islands, 392.
Selection of domestic products, 29.
——, principle not of recent origin, 33.
——, unconscious, 34.
——, natural, 80.
——, sexual, 87.
——, natural, circumstances favourable to, 102.
Sexes, relations of, 87.
Sexual characters variable, 156.
—— selection, 87.
Sheep, Merino, their selection, 31.
——, two sub-breeds unintentionally produced, 36.
——, mountain, varieties of, 76.
Shells, colours of, 132.
——, littoral, seldom embedded, 288.
——, fresh-water, dispersal of, 385
—— of Madeira, 391.
——, land, distribution of, 397.
Silene, fertility of crosses, 257.
Silliman, Prof., on blind rat, 137.
Skulls of young mammals, 197, 436.
Slave-making instinct, 219.
Smith, Col. Hamilton, on striped horses, 164.
——, Mr. Fred., on slave-making ants, 219.
——, on neuter ants, 239.
——, Mr., of Jordan Hill, on the degradation of coast-rocks, 283.
Snap-dragon, 161.
Somerville, Lord, on selection of sheep, 31.
Sorbus, grafts of, 262.
Spaniel, King Charles's breed, 35.
Species, polymorphic, 46.
——, common, variable, 53.
—— in large genera variable, 54.
——, groups of, suddenly appearing, 302, 307.
—— beneath Silurian formations, 307.
—— successively appearing, 312.
—— changing simultaneously throughout the world, 322.
Spencer, Lord, on increase in size of cattle, 35.
Sphex, parasitic, 218.
Spiders, development of, 442.
Spitz-dog crossed with fox, 268.
Sports in plants, 9.
Sprengel, C. C, on crossing, 98.
——, on ray-florets, 145.
Squirrels, gradations in structure, 180.
Staffordshire, heath, changes in, 71.
Stag-beetles, fighting, 88.
Sterility from changed conditions of life, 9.
—— of hybrids, 246.
—— ——, laws of, 255.
—— ——, causes of, 263.
—— from unfavourable conditions, 265.
—— of certain varieties, 269.
St. Helena, productions of, 390.
St. Hilaire, Aug., on classification, 418.
St. John, Mr., on habits of cats, 91.
Sting of bee, 202.
Stocks, aboriginal, of domestic animals, 18.
Strata, thickness of, in Britain, 284.
Stripes on horses, 163.
Structure, degrees of utility of, 201.
Struggle for existence, 60.
Succession, geological, 312.
Succession of types in same areas, 338.
Swallow, one species supplanting another, 76.
Swim-bladder, 190.
System, natural, 413.
T.
Tail of giraffe, 195.
—— of aquatic animals, 196.
——, rudimentary, 454.
Tarsi deficient, 135.
Tausch on umbelliferous flowers, 146.
Teeth and hair correlated, 144.
——, embryonic, traces of, in birds, 450.
——, rudimentary, in embryonic calf, 450, 480.
Tegetmeier, Mr., on cells of bees, 228, 233.
Temminck on distribution aiding classification, 419.
Thouin on grafts, 262.
Thrush, aquatic species of, 185.
——, mocking, of the Galapagos, 402.
——, young of, spotted, 439.
——, nest of, 243.
Thuret, M., on crossed fuci, 258.
Thwaites, Mr., on acclimatisation, 140.
Tierra del Fuego, dogs of, 215.
Timber-drift, 360.
Time, lapse of, 282.
Titmouse, 184.
Toads on islands, 393.
Tobacco, crossed varieties of, 271.
Tomes, Mr., on the distribution of bats, 395.
Transitions in varieties rare, 172.
Trees on islands belong to peculiar orders, 392.
—— with separated sexes, 99.
—— incarnatum, 94.
Trigonia, 321.
Trilobites, 307.
——, sudden extinction of, 321.
Troglodytes, 243.
Tucutucu, blind, 137.
Tumbler pigeons, habits of, hereditary, 214.
——, young of, 446.
Turkey-cock, brush of hair on breast, 90.
Turkey, naked skin on head, 197.
——, young, wild, 216.
Turnip and cabbage, analogous variations of, 159.
Type, unity of, 206.
Types, succession of, in same areas, 339.
U.
Udders enlarged by use, 11.
——, rudimentary, 451.
Ulex, young leaves of, 439.
Umbelliferæ, outer and inner florets of, 144.
Unity of type, 206.
Use, effects of, under domestication, 11.
——, effects of, in a state of nature, 134.
Utility, how far important in the construction of each part, 199.
V.
Valenciennes on fresh-water fish, 384.
Variability of mongrels and hybrids, 274.
Variation under domestication, 7.
—— caused by reproductive system being affected by conditions of life, 8.
—— under nature, 44.
——, laws of, 131.
Variations appear at corresponding ages, 14, 86.
——, analogous in distinct species, 159.
Varieties, natural, 44.
——, struggle between, 75.
——, domestic, extinction of, 111.
——, transitional, rarity of, 172.
——, when crossed, fertile, 268.
——, when crossed, sterile, 269.
——, classification of, 423.
Verbascum, sterility of, 251.
——, varieties of, crossed, 271.
Verneuil, M. de, on the succession of species, 325.
Viola tricolor, 73.
Volcanic islands, denudation of, 285.
Vulture, naked skin on head, 197.
W.
Wading-birds, 386.
Wallace, Mr., on origin of species, 2.
——, on law of geographical distribution, 355.
——, on the Malay Archipelago, 395.
Wasp, sting of, 202.
Water, fresh, productions of, 383.
Water-hen, 185.
Waterhouse, Mr., on Australian marsupials, 116.
——, on greatly developed parts being variable, 150.
——, on the cells of bees, 225.
——, on general affinities, 429.
Water-ouzel, 185.
Watson, Mr. H. C, on range of varieties of British plants, 58.
——, on acclimatisation, 140.
——, on flora of Azores, 363.
——, on Alpine plants, 368, 376.
——, on rarity of intermediate varieties, 176.
Weald, denudation of, 285.
Web of feet in water-birds, 185.
West Indian islands, mammals of, 396.
Westwood on species in large genera being closely allied to others, 57.
—— on the tarsi of Engidæ, 157.
—— on the antennæ of hymenopterous insects, 415.
Wheat, varieties of, 113.
White Mountains, flora of, 365.
Wings, reduction of size, 134.
—— of insects homologous with branchiæ, 191.
——, rudimentary, in insects, 450.
Wolf crossed with dog, 214.
—— of Falkland Isles, 394.
Wollaston, Mr., on varieties of insects, 48.
——, on fossil varieties of land-shells in Madeira, 52.
——, on colours of insects on sea-shore, 132.
——, on wingless beetles, 135.
——, on rarity of intermediate varieties, 176.
——, on insular insects, 389.
——, on land-shells of Madeira, naturalised, 402.
Wolves, varieties of, 90.
Woodpecker, habits of, 184.
——, green colour of, 197.
Woodward, Mr., on the duration of specific forms, 294.
——, on the continuous succession of genera, 316.
——, on the succession of types, 339.
World, species changing simultaneously throughout, 322.
Wrens, nest of, 243.
Y.
Youatt, Mr., on selection, 31.
——, on sub-breeds of sheep, 36.
——, on rudimentary horns in young cattle, 454.
Z.
Zebra, stripes on, 163.